Call button indicator for an elevator



FIG. 1 is a front elevational view of a call button indicator for an elevator showing my new design, with the broken lines showing for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a left side elevational view thereof, with the right side being a mirror image;

FIG. 3 is a top plan view thereof, with the bottom being a mirror image. 

The ornamental design for a call button indicator for an elevator, as shown and described. 